The ET (Eminent Technology) LFT-8b does indeed far exceed the sound quality of any Polk I've ever heard (they're all over SoCal). It's good enough to lead VPI's Harry Weisfeld to proclaim the speaker to have the best midrange of any speaker he has ever heard.
A post above stated as fact that the ET needs a lot of power, which is an overstatement. It's sensitivity spec may lead one to form that presumption, but in practice is not particularly true. The LFT-8b does not require the power the other magnetic-planar speaker, the Magneplanar, does, for instance. I have both ET's and Maggies, and they are as different as they are similar. The LFT-8b is an easy 8 ohm load, your 15ow/ch amp will be fine until you can do better. The ET can even be run with a modestly-powered tube amp, as I do (100w/ch), which is not true of Maggies.